Field of the Invention
The present invention relates to an image forming apparatus.
Description of the Related Art
In a conventional image forming apparatus, since a photosensitive drum is directly supported by a bearing part, when the photosensitive drum is replaced, it is necessary to be disassembled, and its maintenance has not been easy (for example, see JP 05-289588 A).
Therefore, a technology has been devised for ensuring detachment easiness of the photosensitive drum by using: a process frame from which the photosensitive drum is detachable; an apparatus body from which the process frame is removable; a drum shaft including one end constituting a free end and the other end supported by the apparatus body and transmitting rotational driving force to the photosensitive drum; and a fixing member for stopping movement of the photosensitive drum in an axial direction of the drum shaft.
Here, to ensure detachment easiness of the photosensitive drum, it is necessary to provide a fitting gap between the photosensitive drum and the drum shaft, between the drum shaft and the fixing member, and the like. In the process frame, in addition to the photosensitive drum, an imaging unit is also arranged including a developing device, a charging unit, a cleaning device, and the like. The imaging unit is longer than the photosensitive drum in an insertion/removal direction of the process frame to ensure the maximum image area.
As a result, the process frame and the fixing member also become long, and influence is increased of part accuracy of a contact portion of the photosensitive drum and the fixing member (for example, squareness with respect to the drum shaft), and there is a problem that deviation to one side of the fitting gap (a phenomenon in which the fitting gap comes to one side in a radial direction from the contact portion as a point of origin) is caused.
Further, it is necessary to increase contact force to the fixing member and the photosensitive drum to inhibit the photosensitive drum from idly rotating on the drum shaft, and there is a problem that bending is caused of the drum shaft from the contact portion as a point of origin.